This LFCS practice question tests your understanding of networking. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A Linux server is unable to resolve the hostname 'app.internal.example.com' but can resolve other names. The /etc/nsswitch.conf file contains: hosts: files mdns4_minimal [NOTFOUND=return] dns. The /etc/hosts file does not list the hostname. Which configuration change would most likely resolve the issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Remove the mdns4_minimal entry or change it to 'mdns4' without the NOTFOUND=return
The issue is that mdns4_minimal with [NOTFOUND=return] causes the resolver to stop after a failed mDNS query, preventing it from falling back to DNS. Since the hostname is not in /etc/hosts and not reachable via mDNS, the resolver returns 'not found' immediately without querying DNS. Removing the mdns4_minimal entry or changing it to 'mdns4' (without the NOTFOUND=return) allows the resolver to proceed to DNS if mDNS fails.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Change the hosts line to: hosts: dns files mdns4_minimal
Why it's wrong here
This changes order but still has the NOTFOUND=return policy which may stop after mdns.
✗
Configure /etc/resolv.conf to use a different DNS server
Why it's wrong here
DNS resolution is not the primary issue; nsswitch is preventing DNS query.
✓
Remove the mdns4_minimal entry or change it to 'mdns4' without the NOTFOUND=return
Why this is correct
Removing the return policy allows fallback to DNS.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Add the hostname to the local multicast DNS configuration
Why it's wrong here
The hostname is on a different domain and not served by mDNS.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume the issue is with DNS configuration or order, but the real problem is the [NOTFOUND=return] action on mdns4_minimal, which prematurely terminates the resolution chain for non-.local hostnames.
Detailed technical explanation
How to think about this question
The nsswitch.conf 'hosts' database uses service specifications like 'files', 'mdns4_minimal', and 'dns' in order. The '[NOTFOUND=return]' action is a status-based action that tells the resolver to return immediately if the service returns NOTFOUND, skipping subsequent services. In this case, mdns4_minimal only queries for names ending in '.local' (per RFC 6762), so for 'app.internal.example.com', it returns NOTFOUND, and the resolver stops before reaching DNS. Removing the action or using 'mdns4' (which queries all names) would allow fallback to DNS.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the LFCS exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Networking — This question tests Networking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Remove the mdns4_minimal entry or change it to 'mdns4' without the NOTFOUND=return — The issue is that mdns4_minimal with [NOTFOUND=return] causes the resolver to stop after a failed mDNS query, preventing it from falling back to DNS. Since the hostname is not in /etc/hosts and not reachable via mDNS, the resolver returns 'not found' immediately without querying DNS. Removing the mdns4_minimal entry or changing it to 'mdns4' (without the NOTFOUND=return) allows the resolver to proceed to DNS if mDNS fails.
What should I do if I get this LFCS question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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